Kenny Jon-Émile S, Barjaktarevic Igor, Mackenzie David C, Eibl Andrew M, Parrotta Matthew, Long Bradley F, Eibl Joseph K
Health Sciences North Research Institute, Sudbury, ON, P3E 2H2, Canada.
Division of Pulmonary and Critical Care, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
Intensive Care Med Exp. 2020 Sep 17;8(1):54. doi: 10.1186/s40635-020-00339-7.
Change of the corrected flow time (Ftc) is a surrogate for tracking stroke volume (SV) in the intensive care unit. Multiple Ftc equations have been proposed; many have not had their diagnostic characteristics for detecting SV change reported. Further, little is known about the inherent Ftc variability induced by the respiratory cycle.
Using a wearable Doppler ultrasound patch, we studied the clinical performance of 11 Ftc equations to detect a 10% change in SV measured by non-invasive pulse contour analysis; 26 healthy volunteers performed a standardized cardiac preload modifying maneuver.
One hundred changes in cardiac preload and 3890 carotid beats were analyzed. Most of the 11 Ftc equations studied had similar diagnostic attributes. Wodeys' and Chambers' formulae had identical results; a 2% change in Ftc detected a 10% change in SV with a sensitivity and specificity of 96% and 93%, respectively. Similarly, a 3% change in Ftc calculated by Bazett's formula displayed a sensitivity and specificity of 91% and 93%. Ftc had 100% concordance and an R of 0.75 with change in SV; these values were 99%, 0.76 and 98%, 0.71 for Ftc and Ftc, respectively. As an exploratory analysis, we studied 3335 carotid beats for the dispersion of Ftc during quiet breathing using the equations of Wodey and Bazett. The coefficient of variation of Ftc during quiet breathing for these formulae were 0.06 and 0.07, respectively.
Most of the 11 different equations used to calculate carotid artery Ftc from a wearable Doppler ultrasound patch had similar thresholds and abilities to detect SV change in healthy volunteers. Variation in Ftc induced by the respiratory cycle is important; measuring a clinically significant change in Ftc with statistical confidence requires a large sample of beats.
校正血流时间（Ftc）的变化是重症监护病房中追踪每搏输出量（SV）的替代指标。已提出多个Ftc方程；许多方程尚未报告其检测SV变化的诊断特征。此外，关于呼吸周期引起的Ftc固有变异性知之甚少。
我们使用可穿戴式多普勒超声贴片，研究了11个Ftc方程检测通过无创脉搏轮廓分析测量的SV 10%变化的临床性能；26名健康志愿者进行了标准化的心脏前负荷调节操作。
分析了100次心脏前负荷变化和3890次颈动脉搏动。所研究的11个Ftc方程中的大多数具有相似的诊断属性。沃迪（Wodeys）公式和钱伯斯（Chambers）公式结果相同；Ftc 2%的变化检测到SV 10%的变化，敏感性和特异性分别为96%和93%。同样，巴泽特（Bazett）公式计算的Ftc 3%的变化显示敏感性和特异性分别为91%和93%。Ftc与SV变化的一致性为100%，R为0.75；Ftc和Ftc与SV变化的一致性和R值分别为99%、0.76和98%、0.71。作为探索性分析，我们使用沃迪和巴泽特的方程研究了3335次颈动脉搏动在安静呼吸期间Ftc的离散度。这些公式在安静呼吸期间Ftc的变异系数分别为0.06和0.07。
从可穿戴式多普勒超声贴片计算颈动脉Ftc的11个不同方程中的大多数在检测健康志愿者SV变化方面具有相似的阈值和能力。呼吸周期引起的Ftc变化很重要；要以统计学置信度测量Ftc的临床显著变化需要大量的搏动样本。
